Performance of concurrent non-motor tasks in Parkinson's disease.

The purpose of the study was to examine the hypothesis that patients with Parkinson's disease have a general inability to cope with concurrent task demands, and that this inability stems from a lack of attentional control of motor and cognitive activities. Performance on a verbal and on a visuospatial memory task was compared with performance on largely identical memory tasks which were combined with concurrent non-motor tasks. As a further index of a possible weakness of the attentional control of cognitive function order memory was assessed and compared with item memory. Both parkinsonian patients and controls showed a decline of memory performance when the concurrent task was introduced, but the degree of decline did not differ between groups. Parkinsonian patients scored worse than controls on both conditions of the verbal memory task and had more intrusions from previous lists in the verbal single task. There was no significant difference between groups in either item or order memory, but in parkinsonians the scores on order memory decreased with advancing illness. It is concluded that patients with Parkinson's disease do not have a general inability to cope with concurrent task demands, but that the results can be interpreted as indicating a weakness of certain aspects of the attentional control of cognitive function.